1. Field of Invention
The present disclosure relates in general to a device and method for dispensing fuels lighter than air, such as compressed natural gas (CNG). More specifically, the present disclosure relates to a gas dispenser having gas handling components and electronics in the same structure, and where the electronics are mounted in a non-purged housing spaced away from the gas handling components.
2. Description of Prior Art
Traditionally, vehicles have been fueled by one or more distillates of fuel oil, such as gasoline or diesel. Since these fuels have vapors that are heavier than air, the dispensers for these fuels were designed with the electronics located above the fuel-handling, hazardous area. This allowed the dispenser structure to be broken into different hazardous area classifications allowing electronics to be located in the structure with minimal safeguards from the flammable vapors below. Recently, a growing number of vehicles have been manufactured, or converted, to operate on compressed natural gas (CNG), which is lighter than air, instead of the heavier than air longer chain hydrocarbons. The availability, low cost, and lower emissions of combusting natural gas over fuel oil distillates have garnered interest in continuing to increase the number of natural gas powered vehicles. Similar to typical gasoline or diesel fueling dispensers, CNG fueling dispensers, whose structure contains piping and valves for delivering gas to a customer, have been designed using similar dispenser structures with the electronics, which control the dispenser and payment authorization terminals, above the gas handling components.
Standards for the safe handling of CNG have been published by national code recommending bodies. Many states have adopted these codes in their respective vehicle, transportation, and building regulations. As CNG is lighter than air, unlike gasoline or diesel vapors, CNG that may escape from the gas handling components can rise; and thus present different hazardous zones for a CNG dispenser as compared to a gasoline or diesel dispenser. As such, standards for CNG dispensers reflect a different hazardous zone rating as compared to gasoline or diesel dispensers in these standards. For example, explosive vapors may sometimes concentrate in spaces above a gas handling portion of a CNG dispenser having a traditional gasoline or diesel dispenser design. By most standards, the spaces normally having the explosive vapor concentration would be deemed Class I, Division 1, thus prohibiting any device capable of producing a spark. For example, applicable codes typically designate Class I locations to be where a flammable gas or vapor may be present in a sufficient amount to produce an explosion or ignitable mixture. Class I locations are sometimes designated as Division 1 when the flammable gas is likely to exist, such as in quantities sufficient to produce an explosive or ignitable mixture under normal operating conditions. Class I locations are sometimes designated as Division 2 when the flammable gas is not normally present in an explosive concentration, but accidentally exists. Some CNG dispensers having traditional gasoline or diesel dispenser structures address this change in hazardous rating by enclosing electronics in an explosion-proof junction box, including an Intrinsic Safe Barrier (ISB), or disposing electronics in an air purged enclosure protected through pressurization. There are some components used in payments terminals that either due to the need of accessibility to the customer or because of the type of component, cannot be adequately protected by an explosion-proof junction box or an ISB. When this is true, these components are normally protected by an air purge system. Correctly implemented, an air purge system can change the area within the enclosure to a non-hazardous, or unclassified area. Air purge systems can be affected by ambient pressure variations and wind. An air purge system also exposes the electronics to cold and/or moist air that can affect the operation of the components as well as corrode or damage them. It can also inject dirt into the system. The fans used for the source of air for air purge systems must be positioned in a location away from the hazardous area that is created by the dispenser, which increases installation costs and complexity.